The present invention relates generally to flow regulation valves, and more particularly, to a non-stick treatment for use with flow regulator valves adapted to permit substantially free flow through the valve in a first direction, while preventing flow through the valve in a second, opposite direction. Even more particularly, the present invention provides a lubricating coating for use in a duckbill valve to ensure opening of the valve to permit fluid flow in the first direction.
Duckbill valves have been known for some time and have been used in a variety of applications, examples of assemblies incorporating such valves being shown in U.S. Pat. Nos. 4,535,818 and 4,612,960. Such an assembly typically includes a housing into which is mounted a resilient flow regulator member or valve element having as its primary operative components a pair of lips arranged in a converging relationship from an open end at the base of the lips to a normally closed outer end. At the closed end of the regulator, the lips are located adjacent each other so as to define a normally closed slit therebetween. The regulator is mounted within the housing in a sealed relationship so that flow through the housing must pass through the regulator as well. In a first or forward direction, flow enters the housing and passes into the regulator through the open end, moving toward the normally closed end. The flow pressure against the resilient lips opens the slit, allowing the flow to pass out of the regulator and the housing. When flow enters the housing from a second or a reverse direction, the flow contacts the regulator at its normally closed end, with the flow pressure against the resilient lips holding the slit in its closed position, thereby preventing flow through the regulator assembly.
One application for a valve of this type is as part of a medical solution administration set. Such a set is used to deliver fluids such as plasma, medicines, and the like from a fluid supply source, such as a bottle or bag, intravenously to a patient. In such an application, it is particularly desirable to have the resilient flow regulator member open at fluid pressures of 8" of water or less.
In order to ensure that the regulator member responds quickly to small changes in fluid pressure for opening and closing the regulator, the regulator is formed of a very soft material, such as silicone having a durometer of 60 shore A or less. Usually, the regulator is molded with the normally closed end being unslit, and a knife cuts the slit subsequent to the molding operation such that a pair of complementary mating surfaces are defined on the opposing lips.
One problem with forming the regulator of soft elastomeric materials is that such soft materials tend to have an increased tackiness such that the complementary cooperating surfaces on the lips forming the slit may have a tendency to stick to each other. The tendency of the lips to stick to each other is affected by ambient conditions such as temperature and humidity, and sterilization techniques such as gamma radiation, as well as by the amount of time that the cooperating surfaces of the lips are allowed to remain in undisturbed engagement with each other. As a result of the lips sticking to each other, it has proven difficult to ensure consistent performance within a group of regulators produced to the same specifications, and a certain percentage of prior art regulators have been found to resist opening until a pressure greater than a desired maximum pressure, such as 8" of water, is applied. In some cases, an operator must pump fluid at an increased pressure against the regulator to obtain an initial separation of the lips, and occasionally the adhesion between the cooperating surfaces of the lips is such that the valve regulator will resist opening at even very large fluid pressures applied to the open end of the regulator.
Accordingly, there is a need for a fluid regulating valve incorporating a regulator wherein the regulator structure is such that opening of the regulator during fluid flow is ensured.